Electric heater



Jan. 15, 1929.

P. F. APFEL ELECTRIC HEATER Filed Oct. 19, 1925 Wham N EF. ww w M Patented Jan. 155, i929.

UNITED STATES v PHILIP F. APFEL, OF SEATTLE, WASHINGTON.

ELECTRIC HEATER.

Application filed. October 19, 1926.

a My invention relates to electric heaters of the resistance type'primarily for use in heating a current of fluid such as air or water, and relates particularly to the manner of arrang- "111g the resistance element in the heater.

An object of my invention is to provide an electric heater in which the resistance element is well insulated electrically.

Another object of my invention is to provide an electric heater in which the resistance wire and its cooperating insulators are some-. what flexible.

A further object of my invention is to provide a heating element for an electric heater in which a large amount or" resistance wire may be compacted into a small space.

' A further object of my invention is to provide a plurality of perforated insulators thru which the resistance wire can be easily threaded.

' The invention possesses other advantageous features, some of which with the foregoing will be set forth at length in the following description where I shall outline in full that form of the electric heater of my invention, which I have selected for illustration in the drawings accompanyingand forming part of the present specification. In said drawings I have shown one form of electric heater embodying my invention, but it is to be understoodthat- I do not limit myself to such form since the invention, as set forth in the claims, may be embodied in a plurality of forms.

In the drawings:

Fig. l is a section on the median plane of a heater embodying my invention.

Fig. 2 is a cross section on the line 2-2 of F 1.

Fig. Fig. 1.

Fig. 4 is, on the left half, a section on the median plane of one of the insulators shown in Fig. 1, and, on the right half, is an elevation of one of the insulators of Fig. 1.

Fig. 5 is an end view of the insulators shown in Fig. 4.

Figs. 6, 7, 8 and 9 are modified forms of insulators.

My invention preferably comprises a resistanceelement for an electric heat-er including an electrically continuous conductor threaded thru. a plurality of perforations in each of several serially arranged insulators.

The embodiment of my invention shown in the drawings is primarily for use in heating water and includes a nipple 6 attached to the 3 is a cross section on the line of Serial No. 142,547.

water supply and threaded into a T 7. To the uppe threaded end of the T a reducer 8 is screwed and supports a housing pipe 9. A similar reducer 11 is attached to the upper end of the housing pipe and leads to an outlet nipple 12. An enlarged chamber 13 is thus formed between the inlet 6 and the outlet 12.

Means are provided for electrically heating the water or other fluid flowing thru the chamber 13. A thermally conductive tube 14 having a closure 16 at one end thereof is pressed into or otherwise affixed to the T 7 at its other end. Copper or another highly conductive'metal issuitable material for the tube. The lower open end of the tube 14 communicates with an outlet box 17 of the standard type which is held to the lower end of the T 7 by means of suitable screws 18. Tabs 21 are provided on opposite corners of the outlet box 17 for attachment ofa cover,

not shown. An insulating block 19 of porcelain or comparable material'ls held to the box 17 by screws 22. Conductors 23 of electrical current enter the conduit box 17 at a convenient point and are secured by suitable bolts and nuts 24 on the porcelain block 19. The resistance element preferably comprises an electrically continuous conductor 26 which is secured at one end to one of the bolts 24 and,

after passing thru a plurality of cylindrical bead insulators 27, enters the first of a series of insulators 28.

Each of the insulators 28 preferably comprises a cylindrical body made of electrically non-conducting material, such as porcelain, and provided with convex ends. Passing thru each of the cylindrical insulators 28 and preferably in substantial parallelism with the central axis thereof are a plurality of perforations 29 usually of circular cross section. The serially arranged insulators 28 are each provided with the same number of perforations 29 and are arranged within the tube 14 with the corresponding perforations in approximate alinement. The electrical conductor 26 enters a perforation in the first insulator 28, passes thru the corresponding perforations in the series of insulators carried within the tube 14 and emerges from the top in sulator 30. It is then doubled back upon itself and is threaded in the opposite direction thru another alined series of perforations, an adjacent series preferably being used. lVhen the conductor 26 emerges from the lower insulator 28 it is againdoubl d back upon itself and threaded thru an adjacent series of perforations 29, in the original direct-ion. The conductor is threaded back and forth until it has filled all of the perforations 29 and projects from the bottom insulator 28. The mannerof threading the conductor thru the insulators is illustrated in Figs. 1, 2 and 3. Several insulating beads 31 are slipped over the projecting port-ion of the wire 26 and the end is secured beneath the nut 2% securing the other of the pair of conductors 23. By the use of theinsulating beads 28 each of which is provided with a plurality of perforations, the electrical conductor 26 is thoroughly insulated from electrical contact with surrounding metal parts but is free to radiate a large amount of heat.' I I 7 The convex ends on the adjacent insulators permit the wire which is being threaded therethru to adjust itself slightly to allow for any misalinement of the corresponding perform tions 29 and alsopermit portions of the wire to be exposed and radiate heat directly to the conducting tube 1d. The irregular ends also permit a certain amount of flexibility in the complete resistance element so that it can adapt itself readily to variations in contour or alinement of the conducting tube 14. Preferably the insulators 27 are made of suflicient diameter to make a snug fit within the tube 14 and maintain their position by frictional contact with the walls of the tube, eliminating extraneous supporting means. It is considered preferable to have the conductor 26 a continuous wire passed back and forth through the serially arranged insulators as has been described, but it is understood that the wire may not be mechanically continuous but can be several sections united to form an electrically continuous conductor.

Other forms of insulators suchas those shown in Figs. 6 to 9, inclusive, may be used upon occasion when the conditions Warrant it to vary the amount of exposed conducting wire, the flexibility of the complete resistance unit and the ease of threading the insulators. The various individual insulators making up the series included in the heating element may all be of similar configuration, or they may be of different forms. For instance, the insulator shown in Fig; 6 can be used in conjunction with the insulator shown in Fig. 7. Various combinations of the different forms of insulators will suggest themselves as being specially advantageous in various circumstances. a

I claim: 7

1. An electric heater comprising an outer fluid circulating housing having an inlet at one end and an outlet at'the other end, an inner spaced, concentrically disposed conducting sleeve mounted at one end of the housing,

said sleeve beingfclosed at one end, spaced apertured insulating discs frictionally engaged within said sleeve'and a resistance element threaded through the apertured discs.

2. An electric heater comprising an upright tube closed at its upper end; a flexible electric heating element including a plurality of substantially axially alined insulators frictionally retained within said tube; each of said insulators being provided with a plurality of perforations extending therethrough, and a single resistance wire passing a plurality of times back and forth through each insulator, the wire being exposed between successive insulators whereby the element may be flexed.

In testimony whereof I have hereunto set my hand.

PHILIP F. APFEL. 

